Vehicle with hybrid battery pack and human-machine interface and method of monitoring

ABSTRACT

A vehicle includes an electric motor and a battery operable to provide electrical power to the electric motor. The battery system includes a first battery pack and a second battery pack. The first battery pack has a relatively high power density, and the second battery pack has a relatively high energy density. An electronic controller determines a remaining driving range of the first battery pack, and a remaining driving range of the second battery pack. The vehicle has a human-machine interface (HMI) operatively connected to the electronic controller and configured to indicate the remaining driving range of the first battery pack and the remaining driving range of the second battery pack. The controller executes a method of monitoring the battery system.

INTRODUCTION

Electric vehicles may be propelled by electric motors that are poweredsolely by electrical energy provided by rechargeable batteries. Hybridvehicles may also depend in part on rechargeable batteries for motivepower. High power batteries are generally capable of fast charging anddischarging. High energy batteries provide a longer driving range perunit of volume or weight than high power batteries, but are less able toquickly charge and recharge than high power batteries and have morelimited lifetime charging cycles.

SUMMARY

A vehicle includes an electric motor configured to provide motive torqueat wheels of the vehicle, and a battery system operatively connected tothe electric motor. The battery system is operable to provide electricalpower to the electric motor. The battery system includes a first batterypack and a second battery pack. The first battery pack has a relativelyhigh power density in comparison to the second battery pack, and thesecond battery pack has a relatively high energy density in comparisonto the first battery pack. The vehicle also includes an electroniccontroller configured to determine a remaining driving range of thefirst battery pack, and a remaining driving range of the second batterypack. The vehicle has a human-machine interface (HMI) operativelyconnected to the electronic controller and configured to indicate theremaining driving range of the first battery pack and the remainingdriving range of the second battery pack. The HMI may include a displayscreen, in which case the remaining driving range is indicated visually.In other embodiments, the remaining driving range could be indicatedaurally, such as over an audio system.

In this manner, a vehicle operator is made aware of the remainingdriving ranges of both battery packs. Relatively high energy batterypacks are typically less durable and have a lower number of lifetimecharging cycles before the ability to charge the battery pack degrades.Because the operator is made aware of the remaining driving ranges ofboth battery packs, this may encourage the operator to recharge the highpower battery pack more frequently, thus potentially lessening thefrequency of recharging the high energy battery pack and preserving itsuseful life over a longer term, especially in a vehicle in which thecharge of the high power energy pack is used prior to the charge of thehigh energy battery pack to meet driving needs.

In one or more embodiments, the HMI includes at least one displayscreen. The remaining driving range of the first battery pack isdisplayed as a first image on the at least one display screen, and theremaining driving range of the second battery pack is displayed as asecond image on the at least one display screen. The first image andsecond image may be displayed concurrently. For example, the first imagemay be a first rotary gauge, and the second image may be a second rotarygauge. Rotary gauges are often used to display fuel level on vehicleswith internal combustion engines. Accordingly, a vehicle driver may beprompted to recharge earlier when made aware of a low charge level ofthe first battery pack, for example, then if only made aware of thecombined charge level of both battery packs. In other embodiments, theimage may be a number.

In one or more embodiments, the vehicle includes a navigation systemoperatively connectable to the electronic controller. The electroniccontroller is configured to compare the remaining driving range of thefirst battery pack to a predetermined charge alert threshold drivingrange, and determine, via the navigation system, one or more chargestations within a predetermined distance of the vehicle if the remainingdriving range of the first battery pack is less than the predeterminedcharge alert threshold driving range. The electronic controller thencommands the HMI to indicate the one or more charge stations within thepredetermined distance of the vehicle. For example, the HMI may includea display screen, and the HMI may indicate the one or more chargestations within the predetermined distance of the vehicle by listing theone or more charge stations within the predetermined distance of thevehicle on a display screen.

For example, the charge stations may be public and/or commercial chargestations that provide a higher current charge than does a charge at aprivate residence, and thus enable a faster charge, as is appropriatefor a charge occurring during daily use of the vehicle as opposed to anovernight charge which may be slower without inconveniencing the vehicleoperator.

In some embodiments, the vehicle is also equipped to provide informationabout remaining battery life to the vehicle operator. For example, inone or more embodiments, the electronic controller is configured todetect any second battery pack charging event, and command the HMI toindicate a number of remaining charging cycles of the second batterypack based on the second battery pack charging event. The second batterypack charging event detected and tracked by the electronic controllermay be from an external charge source, or may be from a regenerativebraking event.

The electronic controller is able to estimate the remaining chargingcycles of the second battery pack in a number of ways. For example, thesecond battery pack may have a cycle life of a predetermined maximumnumber of charging cycles, each of the charging cycles includingcharging the second battery pack with a maximum amount of energy(Watt-hours) of the second battery. The electronic controller may beconfigured to track lifetime remaining charging cycles of the secondbattery pack. For example, for each second battery pack charging event,whether from an external charge source or due to regenerative braking,the controller may be configured to determine an amount of energyreceived by the second battery pack, determine a ratio of the amount ofenergy received by the second battery pack to the maximum amount ofenergy of the second battery, and decrement the ratio from lifetimeremaining charging cycles. The lifetime remaining charging cycles has aninitial value of the predetermined maximum number of charging cycles.

In one or more embodiments, the controller may determine a roundedlifetime remaining charging cycle value by rounding the lifetimeremaining charging cycles to a nearest whole number. The number ofremaining charging cycles indicated by the HMI is the rounded lifetimeremaining charging cycle value. For example, rounding the lifetimeremaining charging cycles to a nearest whole number may include roundingany lifetime remaining charging cycles value ending in a decimal greaterthan or equal to 0.5 up to the next whole number. Alternatively,remaining charging cycles indicated by the HMI could include fractionsof a remaining charge cycle.

A method of monitoring a battery system for a vehicle includesdetermining, via an electronic controller, a remaining driving range ofthe first battery pack, and a remaining driving range of the secondbattery pack. The first battery pack has a relatively high power densityin comparison to the second battery pack, and the second battery packhas a relatively high energy density in comparison to the first batterypack. The method includes commanding a human-machine interface (HMI)operatively connected to the electronic controller to indicate theremaining driving range of the first battery pack and the remainingdriving range of the second battery pack.

The above features and advantages and other features and advantages ofthe present disclosure are readily apparent from the following detaileddescription of the best modes for carrying out the disclosure when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an electric vehicle having anenergy management system including a hybrid battery pack, and showing aresidential and fast charge station for the vehicle.

FIG. 2 is a schematic illustration of a portion of the energy managementsystem of FIG. 1, including the hybrid battery pack.

FIG. 3 is a schematic illustration of a human-machine interface (HMI)and an electronic controller included in the vehicle of FIG. 1.

FIG. 4 is a schematic illustration of the vehicle of FIG. 1 with anavigation system for indicating surrounding fast charging stations.

FIG. 5 is a flowchart of a method of monitoring the battery system ofthe electric vehicle.

DETAILED DESCRIPTION

Referring to the drawings, wherein like reference numbers refer to likecomponents throughout the views, FIG. 1 shows an electric vehicle 10.The electric vehicle 10 is powered solely by electric power providedfrom a hybrid battery pack 12 to one or more electric machines 14 thatprovide motive force to front vehicle wheels 16 and may be referred toas an “all-electric” vehicle. One electric machine 14 is shownoperatively connected to front wheels 16 via a gearing arrangement 18and half shafts 20. In various embodiments, an additional electricmachine (not shown) may be similarly operatively connected to the rearwheels 19, an electric machine could be connected to the rear wheels 19with no electric machine connected to the front wheels 16, or each wheelmay be operatively connected to a separate electric machine. Rear halfshafts 21 are shown in fragmentary view in FIG. 1. The electric machine14 is configured to be operable as a motor during a driving mode of thevehicle 10, and as a generator such as during regenerative braking ofthe vehicle 10.

Although depicted on an electric vehicle 10, the hybrid battery pack 12,energy management system 22 and method 100 described herein may beapplicable to a hybrid electric vehicle that utilizes the hybrid batterypack to power one or more electric motors for propulsion, and that alsohas an internal combustion engine as a source of motive power (e.g., ahybrid electric vehicle).

The hybrid battery pack 12 is part of an energy management system 22 andmay be referred to as a “hybrid” battery pack as it integrates both arelatively high power (i.e., high power density) first battery pack 24(referred to as a high power battery pack 24 or a power battery pack24), and a relatively high energy (i.e., high energy density) secondbattery pack 26 (referred to as a high energy battery pack or an energybattery pack 26). The hybrid battery pack 12 includes a housing 28 thatsupports and retains both the high power battery pack 24 and the highenergy battery pack 26 in a single, unitary construction. With referenceto FIG. 2, the high power battery pack 24 includes a first set ofbattery cells 24A connected in series and/or parallel with one another(the high power battery cells 24A) and the high energy battery pack 26includes a second set of battery cells 26A connected in series and/orparallel with one another (the high energy battery cells 26A) andadjacent to the high power battery cells 24A in the housing 28.

The energy management system 22 includes an electronic controller 23that executes a method 100 of monitoring the battery system 22 thatinforms the vehicle operator of the state-of-charge of the battery packs24, 26, and the remaining cycle life of the high energy battery pack 26,and may thereby result in the vehicle operator charging the high powerbattery pack 24 more frequently than otherwise, which may elongate thelife of the high energy battery pack 26. The high energy battery pack 26is less durable than the high power battery pack 24 with respect tocharging cycles. Additionally, the high energy battery pack 26 is lessable to receive a “fast” charge (i.e., a relatively high current in arelatively short time period), as may be associated with commercial,non-residential charging stations.

The electronic controller 23 may be used to control ongoing operation ofthe hybrid battery pack 12 via the transmission of control signals toswitches S_(E) and S_(P). When the switch S_(E) is closed, the highenergy battery pack 26 is able to be charged and/or discharged. When theswitch S_(P) is closed, the high power battery pack 24 is able to becharged and discharged. The electronic controller 23 may be embodied asone or more electronic control units having a requisite memory M and aprocessor P, as well as other associated hardware and software, e.g., aclock or timer, input/output circuitry, etc. Memory M may includesufficient amounts of read only memory, for instance magnetic or opticalmemory. Instructions embodying the method 100 may be programmed ascomputer-readable instructions into the memory M and executed by theprocessor P during operation of the vehicle 10.

The energy management system 22 is configured and the method 100 isdesigned so that the high power battery pack 24 is charged anddischarged separately from the high energy battery pack 26. Stateddifferently, the high power battery pack 24 is not used to charge thehigh energy battery pack 26, the high energy battery pack 26 is not usedto charge the high power battery pack 24, the high power battery pack 24may be discharged without discharging the high energy battery pack 26,and the high energy battery pack 26 may be discharged withoutdischarging the high power battery pack 24.

The high energy battery pack 26 has a relatively high energy density incomparison to the high power battery pack 24 (i.e., energy per unit ofweight or per unit of size, such as in kilowatt-hours per kilogram(kWh/kg) or kilowatt-hours per liter (kWh/l)), and extends the range ofthe vehicle 10 in comparison to a battery system having the high powerbattery pack 24 but not the high energy battery pack 26. The high energybattery pack 26 may have a high internal resistance, limiting itsability to accept high current to charge quickly. For example, the highenergy battery pack 26 may have an energy density in kilowatt-hours perkilogram or per liter at least 50% greater than the energy density ofthe high power battery pack. In one embodiment, the high energy batterypack 26 includes Lithium-metal based energy battery cells 26A with 400Wh/kg energy density, and the high power battery pack 24 includeslithium-titanate based battery cells 24A of about 100 Wh/kg energydensity. In this case, the high energy battery pack 26 has about 300%greater specific energy relative to the high power battery pack 24. Inanother embodiment, the high energy battery pack 26 includes Lithium-Ionbased energy battery cells 26A with 250 Wh/kg energy density, and thehigh power battery pack 24 includes Lithium-Ion based battery cells 24Aof about 150 Wh/kg energy density. In this case, the high energy batterypack 26 has about 67% greater specific energy relative to the high powerbattery pack 24.

The high power battery pack 24 has a relatively high power density incomparison to the high energy battery pack 26 (i.e., power per unit ofsize or per unit of weight, such as in kilowatts per kilogram or perliter). For example, the high power battery pack 24 may have a powerdensity in kilowatts per kilogram or per liter at least 100% greaterthan the power density of the high energy battery pack 26. Usingallowable charging rate as a rough estimate of the power density of thebattery packs 24, 26, in an embodiment, the high power battery pack 24includes battery cells 24A that can charge at the 4C rate for 80%state-of-charge (SOC), and the high energy battery pack 26 includesbattery cells 26A that can typically charge at about the C/3 rate. Inthis embodiment, the high power battery pack 24 thus has roughly 1100%greater power density than the high energy battery pack 26. The 1C ratecorresponds to the current needed to charge the battery from a fullydischarged state to the fully charged state in one hour. The 4C ratecorresponds to the current needed to charge the battery from a fullydischarged state to the fully charged state in one quarter of an hour,or 15 minutes.

The high power battery pack 24 has the advantage of an ability to accepthigher current during charging than the high energy battery pack 26,enabling what may be referred to as a “fast” charge that may be obtainedfrom a charge source 31 (also referred to as a charge station, shown inFIG. 1) configured to provide relatively high current. The charge source31 may be, for example, a public charging station rather than a privateresidence. The charge sources 31 may be public charge stations thatprovide a higher current recharge than does a recharge at a privateresidence, and thus enable a faster recharge. Access to such a chargesource 31 enables the vehicle 10 to continue a driving excursion, andprovides a quicker partial or full recharge of the high power batterypack 24, as explained herein.

Placement of a charging device at the charging port 42 is indicative ofa charging event, and the controller 23 is configured to detect acharging event such as by sensors at the charging port 42, and/or bysensors 33 at the battery cells 24A, 26A. Charging devices include thefast charging device 40 or a home charging device 43. The home chargingdevice 43 which provides current through a DC converter 49 connected toan AC charge source 47, such as may be available at an operator's home51 for overnight charging. FIG. 1 shows a fast charging device 40 thatmay be placed at the charge port 42 of FIG. 1 to operatively connect apower supply 44 to the energy management system 22 for recharging thehigh power battery pack 24 and/or the high energy battery pack 26. Ingeneral, if the method 100 prompts the vehicle operator to morefrequently charge the hybrid battery pack 24, less frequent charging ofthe high energy battery pack 26 will occur. Generally, the energymanagement system 22 may prioritize charging and discharging of the highpower battery pack 24 over the high energy battery pack 26 in order toreduce the frequency of charge cycles of the high energy battery pack26.

The high power battery cells 24A are connected in parallel and/or serieswith one another and are constructed to provide or are composed ofmaterials that provide greater power than the high energy battery cells26A, and the battery pack 24 is therefore referred to as the high powerbattery pack or simply the power battery. Example materials for the highpower battery pack 24 include battery cells with a negative electrodecomprising one or more of a lithium titanate (Li_(4+x)T₁₅O₁₂, where0≤x≤3), and various other Li—Ti—O materials (including Li—Ti—Sc—O,Li—Ti—Nb—O, and Li—Ti—Zn—O), or graphite, and a positive electrodecomprising one or more of a nickel manganese cobalt oxide(Ni_(x)Mn_(y)Co_(z)O₂), where the sum of x, y, and z is one), lithiummanganese oxide (LiMn₂O₄ (spinel)), nickel manganese cobalt oxide (NMC),lithium nickel manganese cobalt oxide (LiNiMnCoO₂), and lithium ironphosphate (LiFePO₄).

The high energy battery cells 26A are connected in series and/orparallel with one another and are composed of materials that providegreater energy than the high power battery cells 24A, and the batterypack 26 is therefore referred to as the high energy battery pack orsimply the energy battery. Example materials for the high energy batterypack 26 include battery cells with a negative electrode comprising oneor more of graphite, or of silicon, or of silica, or of rechargeablelithium metal, and a positive electrode comprising one or more of anickel manganese cobalt oxide (Ni_(x)Mn_(y)Co_(z)O₂), where the sum ofx, y, and z is one), lithium manganese oxide (LiMn₂O₄ (spinel)), nickelmanganese cobalt oxide (NMC), lithium nickel manganese cobalt oxide(LiNiMnCoO₂), lithium iron phosphate (LiFePO₄), or a sulfur-basedpositive electrode.

The high power battery pack 24 may be configured to provide apredetermined maximum range of the vehicle 10 when fully charged, and tobe able to receive an amount of power equivalent to a predeterminedfraction of that maximum range during a fast charge (i.e., relativelyhigh current charging) of a predetermined duration.

With reference to FIG. 2, each battery cell 24A, 26A includes an anodeand a cathode (indicated on either side of a membrane 30 shown withdashed lines). One or more sensors 33 are in operative communicationwith each battery cell 24A, 26A and are operatively connected to theelectronic controller 23 either directly or via a battery modulecontroller (not shown). Selected ones of the membranes 30 and sensors 33are indicated with reference numerals in FIG. 2 for clarity in thedrawing. The sensors 33 are configured to monitor battery parametersduring vehicle operation. For example, the sensors 33 may monitorparameters indicative of the respective state-of-charge of each batterycell 24A, 26A, such as voltage, current, temperature, etc. Theelectronic controller 23, or another controller operatively connected tothe electronic controller 23, may include a state-of-charge estimatormodule that determines a state-of-charge based on the sensor data.

With reference to FIG. 2, the energy management system 22 includes afirst switch S_(P) operatively connected to the high power battery pack24, and a second switch S_(E) operatively connected to the high energybattery pack 26. The first switch S_(P) is also referred to as the powerbattery pack switch, and the second switch S_(E) is also referred to asthe high energy battery pack switch. When the first switch S_(P) isopen, the high power battery pack 24 is disconnected from the electricmachine 14 and from the charge port 42. When the first switch S_(P) isclosed, the high power battery pack 24 is operatively connected to theelectric machine 14 (during drive mode) and to the charge port 42(during charge mode). When the second switch S_(E) is open, the highenergy battery pack 26 is disconnected from the electric machine 14 andfrom the charge port 42. When the second switch S_(E) is closed, thehigh energy battery pack 26 is operatively connected to the electricmachine 14 (during drive mode) and to the charge port 42 (during chargemode).

The first switch S_(P) and the second switch S_(E) are both shown inopen positions in FIG. 2. The electronic controller 23 is operativelyconnected to each of the switches S_(E) and S_(P), and is configured toselectively send a separate control signal to each of the switches S_(E)and S_(P) so that the switches S_(E) and S_(P) may be moved from theopen 2 position to a closed position (represented with dashed lines)independently of one another.

FIG. 1 shows the electric machine 14 (i.e., a load) that may be drivenby or charged by either or both of the high power battery pack 24 andthe high energy battery pack 26 depending on the respective positions ofthe first and second switches S_(E) and S_(P). The electric machine 14is depicted as an alternating current (AC) motor. A power inverter 32 isshown disposed between the electric machine 14 and the switches S_(E),S_(P). The power inverter 32 may be a three-phase power inverter withgate drives and a capacitive input filter. The power inverter 32converts direct current (DC) provided from the high power battery pack24 and/or the high energy battery pack 26 to alternating current (AC)for driving the electric machine 14 as a motor, and converts alternatingcurrent to direct current when functioning as a generator duringregenerative braking.

The electronic controller 23 is configured to determine an operatingparameter of the high power battery pack 24 that is indicative of aremaining driving range of the high power battery pack, and an operatingparameter of the high energy battery pack 26 that is indicative of aremaining driving range of the high energy battery pack. For example,based on sensor signals provided by the sensors 33 to the electroniccontroller 23, the electronic controller 23 determines operatingparameters of the battery cells 24A, 26A indicative of the respectivestate-of-charge of each battery cell 24A, 26A, such as voltage, current,temperature, etc.

As shown in FIG. 3, the vehicle 10 is equipped with a human-machineinterface (HMI) 54 and a navigation system 56, both of which areoperatively connected to the electronic controller 23. The human-machineinterface (HMI) 54 is configured to indicate the remaining driving rangeof the high power battery pack 24 and the remaining driving range of thehigh energy battery pack 26. In the embodiment shown, the HMI 54includes a display screen 58 such as on a dashboard 59 of the vehicle10. The remaining driving range of the high power battery pack 24 isdisplayed as a first image 60 on the display screen 58, and theremaining driving range of the high energy battery pack 26 is displayedas a second image 62 on the display screen 58. An identifier 60A such asa label or image identifies the image 60 as the Power Battery DrivingRange or similar identifier. An identifier 62A such as a label or animage identifies the image 62 as the Energy Battery Driving Range orsimilar identifier.

The first image 60 and second image 62 may be displayed concurrently.For example, the first image 60 is shown as a first rotary gauge, andthe second image 62 is shown as a second rotary gauge. The remainingdriving range of the high power battery pack 24 is indicated by theposition of a needle 63 between an empty position (E) representing azero state-of-charge of the high power battery pack 24, and a fullposition (F), representing a 100 percent state-of-charge of the highpower battery pack 24. A similar needle 63 indicates that remainingdriving range of the high energy battery pack 26. It should beappreciated that the charge capacity of the high power battery pack 24and the charge capacity of the high energy battery pack 26 may decreasewith time, so that a reading of full (i.e., the needle 63 at the fullposition (F)) at the beginning of the cycle life of the battery pack 24may be greater than later in the cycle life of the battery pack 24(i.e., after many charge cycles). A single display screen 58 is shown;however, the HMI 54 may instead include multiple display screens, suchas a separate display screen for the remaining driving range for each ofthe battery packs 24, 26. Additionally, although shown on the dashboard59, the one or more display screens 58 may be positioned elsewhere. Forexample, the one or more display screens may be a heads-up display, suchas a projection on the vehicle windshield. Still further, the indicationof the remaining driving range of the high power battery pack 24 and orthe high energy battery pack 26 may be provided as an audio alertinstead of a visual image. For example, the controller 23 may cause thevehicle audio system to announce the remaining driving range of eachbattery pack 24, 26 when requested, such as by the vehicle operatorpushing a button or making a voice command to request the remainingdriving range.

With reference to FIG. 4, the navigation system 56 may include anantenna 61 and a global positioning system receiver 65 mounted on thevehicle 10 and operatively connectable to the electronic controller 23.The receiver 65 may wirelessly communicate with multiple satellites 66(one shown) so that the electronic controller 23 determines thecoordinate location of the vehicle 10, and fast charge stations 31 thatare within a predetermined distance from the vehicle 10. For example,the electronic controller 23 is configured to compare the remainingdriving range of the high power battery pack 24 to a predeterminedcharge alert threshold driving range, and determine, via the navigationsystem 56, one or more charge stations 31 within a predetermineddistance of the vehicle 10 if the remaining driving range of the highpower battery pack 24 is less than the predetermined charge alertthreshold driving range. The predetermined distance of these chargestations 31 from the vehicle 10 is less than the predetermined chargealert threshold driving range so that the vehicle 10 may be charged at aselected one of these charge stations 31 before the high power batterypack 24 discharges to a minimum state-of-charge.

The electronic controller 23 then commands the HMI 54 to indicate theone or more charge stations 31 within the predetermined distance of thevehicle. For example, in response to a control signal from theelectronic controller 23, the HMI may include an image 64 that includesan identifier 64A, “Suggested Charge Stations” or similar label, andlists the one or more charge stations 31 within the predetermineddistance of the vehicle 10. For example, the names 66A, 66B, 66C ofvarious charge stations may be listed. The address or directions 68A,68B, 68C to each station may be listed, or may be available by touch ona selected one of the names, or by stating the name in a voice-activateddisplay 58. The navigation system 56 is able to provide the directionsbased on the current location of the vehicle 10 and a stored database oflocations of charge stations 31 that is accessed by the navigationsystem 56.

The predetermined charge alert threshold driving range and theassociated predetermined distance of the charge stations 31 from thevehicle 10 may be selected to exceed an average distance between chargestations 31, and may vary based on the global position of the vehicle10. For example, in some localities, there may be fewer charge stations31, and the charge stations 31 may be spaced further apart from oneanother on average. When the vehicle 10 is in such locations, thepredetermined charge alert threshold driving range may be set higher toprompt the vehicle operator to consider recharging at a higher remainingcharge of the high power battery pack 24 than when the vehicle 10 is inthe vicinity of more closely located charge stations 31.

The electronic controller 23 is also configured to detect a high energybattery charging event in order to provide information about remainingbattery life to the vehicle operator. The sensors 33 may detect thestate-of-charge of the battery cells 24A, 26A, and, by monitoringchanges in the state-of-charge over time, detect full and partialdischarges and charges in order to track charging cycles of the batterypacks 24, 26.

The electronic controller 23 may command the HMI 54 to indicate a numberof remaining charging cycles of the high energy battery pack 26 based onthe high energy battery pack charging event. For example, as shown inFIG. 3, in response to a control signal from the electronic controller23, the display 58 also provides an image 70 of the number of remainingcharging cycles. An identifier identifier 70A such as a label or imageidentifies the image 70 as the Energy Battery Remaining Charging Cycles.In the embodiment shown, the image 70 is a numerical value. As chargingcycles occur, the numerical value is decreased. Accordingly, the image70 is similar to an odometer operating in reverse, except that chargingcycles are counted rather than miles driven. Alternatively, or inaddition, a rotary gauge similar to those shown in images 60 and 62 maybe used.

The electronic controller 23 can estimate the remaining charging cyclesof the high energy battery pack 26 in a number of ways. For example, thehigh energy battery pack 26 may have a cycle life of a predeterminedmaximum number of charging cycles, each of the charging cycles includingcharging the high energy battery pack 26 with a maximum amount of energy(kilowatt-hours) of the high energy battery pack 26. The electroniccontroller 23 may be configured to track lifetime remaining chargingcycles of the high energy battery pack 26.

For example, for each second battery charging event, the controller 23may be configured to determine an amount of energy received by the highenergy battery pack 26, determine a ratio of the amount of energyreceived by the high energy battery pack 26 to the maximum amount ofenergy of the high energy battery pack 26, and decrement the ratio fromlifetime remaining charging cycles. The lifetime remaining chargingcycles has an initial value of the predetermined maximum number ofcharging cycles. For example, in the embodiment shown, the predeterminedmaximum number of charging cycles of the high energy battery pack 26 is250. The predetermined maximum number of charging cycles may be based ontest data from testing in which test high energy battery packs 26 aresubjected to repeated charge and discharge, and the predeterminedmaximum number of charging cycles may be an average based on the testdata.

In the embodiment of FIG. 3, the HMI 54 displays the lifetime remainingcharge cycle value as a whole number. The controller 23 may determine arounded lifetime remaining charging cycle value by rounding the lifetimeremaining charging cycles to a nearest whole number, and the number ofremaining charging cycles the HMI 54 is commanded to display is therounded lifetime remaining charging cycle value. For example, roundingthe lifetime remaining charging cycles to a nearest whole number mayinclude rounding a lifetime remaining charging cycles value ending in adecimal greater than or equal to 0.5 up to the next whole number. Inother embodiments, remaining charge cycles could be displayed asincluding fractions of a remaining charging cycle.

As described with respect to vehicle 10, the controller 23 executes amethod 100 of monitoring a battery system 22 for an electric vehicle.The method 100 is depicted as a flow diagram in FIG. 5. Various blocksshown in the flow diagram depicting method steps described herein may beperformed by the controller 23 in a different order than shown, or someof the steps may be formed simultaneously. The method 100 may begin withstep 102, in which the controller 23 determines a remaining drivingrange of the high power battery pack 24, and a remaining driving rangeof the high energy battery pack 26, as previously described.

In step 104, the controller 23 then commands the HMI 54 to indicate theremaining driving range of the high power battery pack 24 and theremaining driving range of the high energy battery pack 26. FIG. 3depicts one embodiment of a display 58 by which the remaining drivingranges are indicated. More specifically, the remaining driving rangesare indicated as images 60, 62 of rotary gauges as described herein.

Next, in step 106, the controller 23 compares the remaining drivingrange of the high power battery pack 24 to a predetermined charge alertthreshold driving range. More specifically, the controller 23 determineswhether the remaining driving range of the high power battery pack 24 isless than the predetermined charge alert threshold driving range. If theremaining driving range of the high power battery pack 24 is less thanthe predetermined charge alert threshold driving range, then the method100 moves to step 108, and the controller 23 determines, via thenavigation system 56, one or more fast charge stations 31 within apredetermined distance of the vehicle 10, and then, in step 110,commands the HMI 54 to indicate the one or more charge stations 31within the predetermined distance of the vehicle 10, such as by listingthem on a display 58, as described with respect to FIG. 3. In thedrawings, “Y” represents an affirmative answer to a query, and “N”represents a negative answer.

Following step 106, if the remaining driving range of the high powerbattery pack 24 is not less than the predetermined charge alertthreshold driving range, or following step 110 if remaining drivingrange of the high power battery pack 24 is less than the predeterminedcharge alert threshold driving range, the electronic controller 23detects the occurrence of a high energy battery pack 26 charging eventin step 112. In step 114, the controller 23 determines an amount ofenergy received by the high energy battery pack 26 in the chargingevent, and then in step 116 determines a ratio of the amount of energyreceived by the high energy battery pack 26 to the maximum amount ofenergy of the high energy battery pack 26, as described herein.

Next, in step 118, the controller 23 decrements the ratio from lifetimeremaining charging cycles. The electronic controller 23 is configured totrack lifetime remaining charging cycles of the high energy battery pack26 by, for each high energy battery pack 26 charging event, determininga rounded lifetime remaining charging cycle value by, in step 120,rounding the lifetime remaining charging cycles to a nearest wholenumber. In step 122, the controller 23 then commands the HMI 54 toindicate a number of remaining charging cycles of the high energybattery pack 26 based on the high energy battery pack 26 charging event.The number of remaining charging cycles the HMI 54 is commanded todisplay is the rounded lifetime remaining charging cycle value. Roundingthe lifetime remaining charging cycles to a nearest whole number mayinclude rounding lifetime remaining charging cycles value ending in adecimal greater than or equal to 0.5 up to the next whole number. Thelifetime remaining charging cycles may have an initial value of thepredetermined maximum number of charging cycles as explained herein.

While the best modes for carrying out the disclosure have been describedin detail, those familiar with the art to which this disclosure relateswill recognize various alternative designs and embodiments forpracticing the disclosure within the scope of the appended claims.

What is claimed is:
 1. A vehicle comprising: an electric motorconfigured to provide motive torque at wheels of the vehicle; a batterysystem operatively connected to the electric motor and operable toprovide electrical power to the electric motor, the battery systemincluding a first battery pack and a second battery pack, the firstbattery pack having a relatively high power density in comparison to thesecond battery pack, and the second battery pack having a relativelyhigh energy density in comparison to the first battery pack; anelectronic controller configured to determine a remaining driving rangeof the first battery pack, and a remaining driving range of the secondbattery pack; and a human-machine interface (HMI) operatively connectedto the electronic controller and configured to indicate the remainingdriving range of the first battery pack and the remaining driving rangeof the second battery pack.
 2. The vehicle of claim 1, wherein: the HMIincludes at least one display screen; the remaining driving range of thefirst battery pack is displayed as a first image on the at least onedisplay screen; and the remaining driving range of the second batterypack is displayed as a second image on the at least one display screen.3. The vehicle of claim 2, wherein the first image and the second imageare displayed concurrently.
 4. The vehicle of claim 2, wherein the firstimage is a first rotary gauge, and the second image is a second rotarygauge.
 5. The vehicle of claim 1, further comprising: a navigationsystem operatively connectable to the electronic controller; wherein theelectronic controller is configured to: compare the remaining drivingrange of the first battery pack to a predetermined charge alertthreshold driving range; determine, via the navigation system, one ormore charge stations within a predetermined distance of the vehicle ifthe remaining driving range of the first battery pack is less than thepredetermined charge alert threshold driving range; and command the HMIto indicate the one or more charge stations within the predetermineddistance of the vehicle.
 6. The vehicle of claim 5, wherein: the HMIincludes a display screen; the HMI indicates the one or more chargestations within the predetermined distance of the vehicle by listing theone or more charge stations within the predetermined distance of thevehicle on the display screen.
 7. The vehicle of claim 1, wherein theelectronic controller is configured to: detect any second battery packcharging event; and command the HMI to indicate a number of remainingcharging cycles of the second battery pack based on the second batterycharging event.
 8. The vehicle of claim 7, wherein: the second batterypack has a cycle life of a predetermined maximum number of chargingcycles, each of the charging cycles including charging the secondbattery pack with a maximum amount of energy (Watt-hours) of the secondbattery pack; and the electronic controller is configured to tracklifetime remaining charging cycles of the second battery pack by, foreach second battery pack charging event: determining an amount of energyreceived by the second battery pack; determining a ratio of the amountof energy received by the second battery pack to the maximum amount ofenergy of the second battery pack; and decrementing the ratio fromlifetime remaining charging cycles, wherein the lifetime remainingcharging cycles has an initial value of the predetermined maximum numberof charging cycles.
 9. The vehicle of claim 8, wherein the electroniccontroller is further configured to track lifetime remaining chargingcycles of the second battery pack by, for each second battery packcharging event: determining a rounded lifetime remaining charging cyclevalue by rounding the lifetime remaining charging cycles to a nearestwhole number; and wherein the number of remaining charging cycles theHMI is commanded to display is the rounded lifetime remaining chargingcycle value.
 10. The vehicle of claim 9, wherein rounding the lifetimeremaining charging cycles to a nearest whole number includes roundingany lifetime remaining charging cycles value ending in a decimal greaterthan or equal to 0.5 up to the next whole number.
 11. A method ofmonitoring a battery system for a vehicle, the method comprising:determining, via an electronic controller, a remaining driving range ofa first battery pack, and a remaining driving range of a second batterypack; wherein the first battery pack has a relatively high power densityin comparison to the second battery pack, and the second battery packhas a relatively high energy density in comparison to the first batterypack; and commanding a human-machine interface (HMI) operativelyconnected to the electronic controller to indicate the remaining drivingrange of the first battery pack and the remaining driving range of thesecond battery pack.
 12. The method of claim 11, wherein: the HMIincludes at least one display screen; the remaining driving range of thefirst battery pack is displayed as a first image on the at least onedisplay screen; and the remaining driving range of the second batterypack is displayed as a second image on the at least one display screen.13. The method of claim 12, wherein the first image and the second imageare displayed concurrently.
 14. The method of claim 12, wherein thefirst image is a first rotary gauge, and the second image is a secondrotary gauge.
 15. The method of claim 11, further comprising: comparingthe remaining driving range of the first battery pack to a predeterminedcharge alert threshold driving range; determining, via the navigationsystem, one or more charge stations within a predetermined distance ofthe vehicle if the remaining driving range of the first battery pack isless than the predetermined charge alert threshold driving range; andcommanding the HMI to indicate the one or more charge stations withinthe predetermined distance of the vehicle.
 16. The method of claim 15,wherein: the HMI includes a display screen; and the HMI indicates theone or more charge stations within the predetermined distance of thevehicle by listing the one or more charge stations within thepredetermined distance of the vehicle on the display screen.
 17. Themethod of claim 11, further comprising: detecting any second batterypack charging event; and commanding the HMI to indicate a number ofremaining charging cycles of the second battery pack based on the secondbattery pack charging event.
 18. The method of claim 17, wherein thesecond battery pack has a cycle life of a predetermined maximum numberof charging cycles, each of the charging cycles including charging thesecond battery pack with a maximum amount of energy (Watt-hours) of thesecond battery pack; and the method further comprising, for each secondbattery pack charging event: determining an amount of energy received bythe second battery pack; determining a ratio of the amount of energyreceived by the second battery pack to the maximum amount of energy ofthe second battery pack; and decrementing the ratio from lifetimeremaining charging cycles, wherein the lifetime remaining chargingcycles has an initial value of the predetermined maximum number ofcharging cycles.
 19. The method of claim 18, wherein the electroniccontroller is further configured to track lifetime remaining chargingcycles of the second battery pack by, for each second battery packcharging event: determining a rounded lifetime remaining charging cyclevalue by rounding the lifetime remaining charging cycles to a nearestwhole number; wherein the number of remaining charging cycles the HMI iscommanded to display is the rounded lifetime remaining charging cyclevalue.
 20. The method of claim 19, wherein rounding the lifetimeremaining charging cycles to a nearest whole number includes roundingany lifetime remaining charging cycles value ending in a decimal greaterthan or equal to 0.5 up to the next whole number.